# File lib/rvg/rvg.rb, line 140
    def background_image=(bg_image)
        warn "background_image= has no effect in nested RVG objects" if @nested
        if bg_image && ! bg_image.kind_of?(Magick::Image)
            raise ArgumentError, "background image must be an Image (got #{bg_image.class})"
        end
        @background_image = bg_image
    end